This invention is related to an improved high efficiency heat exchanger of the type disclosed in U.S. Pat. Nos. 4,311,191 and 4,311,192; each issued on Jan. 19, 1982 in the name of Gerry Vandervaart. Other patents directed to high efficiency heat exchangers of Gerry Vandervaart include U.S. Pat. No. 4,461,345 issued on Jul. 24, 1984; U.S. Pat. No. 4,825,664 issued on May 2, 1989; and U.S. Pat. No. 4,995,241 issued on Feb. 26, 1991.
The heat exchangers disclosed in the latter patents all include conventional components, such as a compressor, indoor and outdoor coils, blowers associated with the coils, a reversing/ expansion valve, and appropriate tubing or conduits through which a heat exchanger medium/refrigerant (Freon) can flow in opposite directions during the air conditioning/cooling mode operation on the one hand and the heating/heat-augmenting mode of operation on the other. Traditionally, conventional heat exchangers reversed operation for cooling and heating modes, but in these patents there is additionally disclosed a heat-augmenting mode of operation in which a gas burner directs flames against the outdoor coil as liquid refrigerant flows therethrough. The liquid refrigerant (Freon) absorbs the heat/Btu's which increases its temperature resulting in a vapor phase exiting the outdoor coil which is subsequently transferred to the indoor coil and utilized with its associated blower to heat the interior of a building or the like.
Though these heat exchangers are extremely efficient, they offer only three modes of operation, and though this is a vast improvement over the prior art which heretofore lacked the heat-augmenting mode of operation, it is desirable to, if possible, increase the heat exchanger efficiency. One approach is that disclosed most recently in U.S. Pat. No. 4,995,241 which utilizes a secondary flue gas absorber coil positioned between the main outdoor coil and a gas burner. The flue gases from flames of the gas burner pass through the coils of the secondary flue gas absorber and any liquid in the latter continues to boil-off as it absorbs heat from the flue gases and this keeps the secondary flue gas absorber coils relatively cold. By the time the flue gases pass through, above and beyond the secondary flue gas absorber coil, they are quite cold and transform the heat-exchange medium within the secondary flue gas absorber coil into a hot vapor which increases the overall efficiency of the entire system, as compared to a heat exchanger absent the secondary flue gas absorber.